# How do I obtain the bode plot of the given transfer function?

7 views (last 30 days)
bebo on 29 Nov 2023
Answered: Sam Chak on 29 Nov 2023
Given the transfer function below, how can I graph it on Matlab to get the bode plot? provide code pls!

Angelo Yeo on 29 Nov 2023
Here is a simple example. You can further put your parameters in H.
s = tf('s');
H = (s+1)/(s^2+s+1);
bodeplot(H)
grid on; zoom on;
bebo on 29 Nov 2023
Edited: Walter Roberson on 29 Nov 2023
This is the code I have so far I broke the equation into parts so it's easier to plug in but I'm still getting an error message.
% Parameters of the boost converter
Vin = 75; % Input voltage
Vout = 150; % Output voltage
L = 7.5e-5; % Inductance
C = 5.01e-4; % Capacitance
R = 30; % Load resistance
fs = 100000; % Switching frequency
D = 0.5; % Duty cycle
rC = .005; %ESR
rL = .1; %ESR
% Equation broken into parts
X = (Vout(R+2*rC))/(L*C(R+rC));
Y = (s+1)/(C(R/2+rC));
Z = (s^2+C(rL(R+rC)+R*rC(1-D)^2)+L)/(L*C(R+rC));
A = (s+(1-D)^2*R+rL)/(L*C(R+rC));
s = tf('s');
H = X(Y/Z*A);
bodeplot(H)
grid on; zoom on;
Walter Roberson on 29 Nov 2023
MATLAB does not have implied multiplication anywhere -- not even in the interal language of the moisture vaporators.
If you want multiplication, you need to use the .* or * operator.

Sam Chak on 29 Nov 2023
You need to improve your skills in identifying math operators. There are many missing '*' operators
% Parameters of the boost converter
Vin = 75; % Input voltage
Vout = 150; % Output voltage
L = 7.5e-5; % Inductance
C = 5.01e-4; % Capacitance
R = 30; % Load resistance
fs = 100000; % Switching frequency
D = 0.5; % Duty cycle
rC = .005; % ESR??
rL = .1; % ESR??
% Equation broken into parts
X = (Vout*(R+2*rC))/(L*C*(R+rC));
% ^ ^
s = tf('s');
Y = (s+1)/(C*(R/2+rC));
% ^
Z = (s^2+C*(rL*(R+rC)+R*rC*(1-D)^2)+L)/(L*C*(R+rC));
% ^ ^ ^ ^
A = (s+(1-D)^2*R+rL)/(L*C*(R+rC));
% ^
H = X*(Y/Z*A);
% ^
bodeplot(H)
% grid on; zoom on;

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